US2158443A - Producing vitreous enameling stock and the like - Google Patents

Description

Passed May 16, 1939 UNITED STATES PRODUCING VITREOUS AND TH ENAMELING STOCK E LIKE Gordon L. von Planck, San Francisco, Calif.

No Drawing. Application November 18, 1936,

- Serial No. 111,488

2.' Claims.

The invention aims to produce an improved vitreous enamelingstock and similar low metalloid steels. Vitreous enameling sheets are commonly made of low metalloid eiiervescing type steel, poured into the ingot molds in-a live condition, without deoxidation, so that the evolution of gas proceeds in the ingot mold while the steel is solidifying, and the steel is characterized by a rimming-in action. Such steel, known as rimming or rimmed steel, contains substantial amounts of various gases soluble ,at high temperatures while the steel is liquid, but soluble in a much lesser degree in solid steel at low temperatures. When this type of steel is used for enameling purposes, it is frequently characterized by a. reboiling action; that is, gas is liberated from the metal base in the process of firing the vitreous enamel coating at high temperatures. This gas bubbles through. the molten enamel g0 coating, the smaller bubbles becoming entrapped in the enamel, resulting in minute blisters which mar the smooth surface of the enamel. This defect, known as boiling or reboiling, requires the greatest of care to eliminate or minimize, by close 5 control, firing temperatures, enamels, etc. Even with close control this defect is responsible for considerable-scrap loss in the enameling process.

This reboiling action and certain other defects v80 in steel sheets of thischaracter are eliminated or greatly mitigated by the present invention.

Low metalloid steel, by which term is meant a steel containing extremely low percentages of elements other than iron, as produced in an open .86 hearth furnace, tends. to build up an oxygen conpreliminary deoxidation, the product is commonly called rimming steel. Deoxidation is the process of adding to the live steel a substance which has, under the conditions prevailing at the time of the addition, a greater affinity for oxygen than has carbon. Deoxidation has the efl'ect of causing the bubbling and effervescing to cease, 55 so that the mass of molten steel lies quiescent.

When deoxidation is complete, the steel is commonly referred to as killed. Products formed by the interaction of the commonly used deoxidizers and oxygen are small particles of liquids or solids which are insoluble, or only slightly soluble, in the molten steel. These deoxidation products are of lesser density than the steel itself, so that they tend to float to the upper surface. If the steel cools and solidifies before the deoxidation products have floated to the top, they are entrapped, and carried through to the finished products as non-- metallic inclusions.

The quantity of deoxidation products formed is roughly proportional to the amount of the oxygen present in the, steel just before deoxidation; and when the quantity of deoxidation products is large, it is difiicult to remove these from the bath, to produce a steel substantially free from inclusions. Since the oxygen content of low metalloid steel is relatively high, it has been difiicult to produce deoxidized low metalloid steel of an acceptable degree of cleanliness, whereas by use of my invention, nosuch obstacle remains. It should be noted that low metalloid steel containing large inclusions cannot be used successfully for enameling purposes, because the large inclusions promote the formationof blisters in the finished product.

According to this invention, calcium and silicon are used for deoxidizing steel of the type described, and steel of greatly improved properties results. It is substantially non-reboiling whenused for enameling; its cleanliness is of a high order when ordinary care is practiced in its pro-' duction; and it may be converted into sheets without the difliculties encountered in the rolling of low metalloid steel killed by other methods, such for example as the formation of cracked edges in rolling. The calcium and sili- 001! may be used with other materials such as ferro-titanium, for example. The calcium and silicon with or without the ferro-titanium, may

be added in the ladle, with the subsequent addition of other.known deoxidizers in the mold.

Or the calcium and the silicon with or without the ferro-titanium may be added in the mold during the teeming operation, and other known deoxidizers added also in the mold. Or the calcium and the silicon with or without ferro-tita-' nium may be added partly in the ladle and partly in the mold.

Preferably the calcium and silicon are added in the form of an alloy which may contain for example to per cent of calcium and to per cent of silicon. The usual methods may be followed in the open hearth for producing fully rimmed steel. Such a steel, for instance, would -contain carbon from .01 to .03 per cent, man- 5 ganese from .05 to .08 per cent, sulphur from .010 to .040 per cent, phosphorus from .010 to .040 per cent, and adding about 6 ounces of aluminum per ton and 2 pounds of ferro-titanium per ton in the. ladle. In teeming from the ladle into the 10 ingot molds the calcium-silicon alloy in crushed form is added gradually while the mold is filling. There maybe added also crushed ferro-titanium alloy. The quantity of calcium-silicon alloy may be varied. Amounts have been tried varying between 43 ounces and '75 ounces per ton of steel, all cases showing non-reboiling characteristics in the metal. A number of top-poured cylindrical ingots have been produced each weighing approximately 3,000 lbs. In the teem- 2o ing of some of these, 64 ounces of calcium-silicon alloy for each ingot was added to the steel while teeming from the ladle into the ingot mold. Other ingots have been produced in the teeming of which 112 ounces of calcium-silicon alloy for each ingot was added; and still others have been produced adding 64 ounces of calcium-silicon alloy and 16 ounces of ferro-titanium in the same manner. The calcium-silicon alloy used had the approximate composition per cent of calcium 30 and 65 per cent of silicon, and the ferro-titanium had the approximate composition 16 per cent titanium, 5 per cent carbon, balance iron. In the .case of all these ingots there was no visible reaction in the mold; the steel remained quiet 5 and solidified with the piped structure characteristic of killed steel. Ingots made in this way require a cropping of about 16 per cent to eliminate the pipe. The sheet bar and sheets roll very satisfactorily with no more than the usual scrap loss in rolling.

Although the preferred method is to add calcium and silicon to the steel in the form of a single alloy, calcium and silicon may be added separately, in close succession, either in the order named or in the reverse order, and either in the form of alloys or as separate elements.

It is probable that the removal of non-metallic inclusions or the reduction of them to a minimum is due to the formation of a fusible calciumsilicate slag which rises to the top of the ingot together with most of the impurities.

Sheets of this non-reboiling type of steel provide a highly desirable stock for the commercial production of enameled goods. They permit such production rapidly in quantities and without necessity for the care and inspection which are involved in enameling sheets produced by the present common methods. culated to eliminate'or greatly reduce the reboiling characteristics have been tried, but the sheets produced have generally been difficult to roll, the rolling involving high scrap losses so as to make the production of them undesirable from a commercial standpoint. This is not the case with stock produced by the method of this invention.

Various modifications of and additions to the specific process described may be made by those skilled in the art without departing from the invention as defined in the-following claims.

What I claim is:

1. The method of manufacturing d-egasified and deoxidized low metalloid steel adapted for use as vitreous enameling stock which comprises forming a bath of low metalloid steel, incorporating therein a proportion of titanium to partially deoxidize and degasify the bath, pouring the same into a mold to solidify and incorporating in the metal in the mold'a sufiicient amount of calcium and silicon to completely degasify and deoxidize the metal, the relative proportions of the calcium and silicon being such as to form readily fusible calcium-silicate compounds.

2. The method of manufacturing a non-reboiling steel for use as vitreous enameling stock which comprises forming a molten bath of steel containing carbon .01 to .03%, manganese .05 to .08%, sulphur and phosphorus not over .04% each, deoxidizing and degasifying the bath with aluminum and titanium, pouring the metal into a mold and incorporating within the metal in the mold a proportion of calcium and silicon in an amount sufiicient to completely deoxidize and degasify the metal and in such relative amount one to the other to form a readily fusible calcium silicate alloy.

GORDON L. VON PLANCK.

Other methods, cal- I